1. Field of the Invention
The present invention relates generally to an apparatus and method for extracting the aspect ratio of received broadcast content and, more particularly, to an apparatus and method for extracting the aspect ratio of received broadcast content, which analyze the frequency of the image of the broadcast content received from a digital broadcasting station, compare the analyzed frequency with a preset threshold value, and extract the aspect ratio of the image, thus enabling the image to be displayed in conformity with the extracted aspect ratio.
2. Description of the Related Art
Standards by which broadcasting stations transmit analog broadcast content include the National Television System Committee (NTSC) standard, the Phase Alternation Line (PAL) standard, and the Sequentiel Couleur Avec Memoire (SECAM) standard.
The NTSC standard is a color Television (TV) broadcasting standard that is used in the U.S., Canada, Mexico, Japan, South Korea, etc. In this standard, the number of scanning lines is 525, and the number of frames transmitted per second is 30.
The PAL standard is a broadcasting standard that is used in Europe, Australia, China, North Korea, etc. In this standard, the number of scanning lines is 625, and the number of frames transmitted per second is 30. This standard is advantageous in that it is not affected by phase distortion that is generated on a transmission path.
The SECAM standard is a broadcasting standard in which color difference signals are sequentially alternated on alternate scanning lines. This standard does not have the disadvantage of image distortion due to frequency and amplitude, but has the disadvantage of degraded vertical resolution.
As described above, the conventional analog TV broadcasting standards used in the world differ in the number of scanning lines, the number of frames transmitted per second, the modulation scheme, the bandwidth of a channel, the bandwidth of an image signal and audio channel modulation. In order to view foreign broadcasts based on a different broadcasting standard, a separate conversion device is required.
Meanwhile, there is digital TV (high definition television) technology that provides image quality similar to that of 35 mm movies and sound quality similar to that of Compact Disks (DCs). The digital TV technology is the technology of transmitting and displaying digital signals instead of analog signals, where the digital signals are compressed and transmitted using Moving Picture Experts Group (MPEG)-2 technology.
As described above, digital TV technology-based broadcasting is the digital broadcasting technology of processing digitized data. A digital TV includes a module for receiving data from digital broadcasting stations and processing the data, and a display window for displaying the processed data.
The principal difference between analog broadcasting and digital broadcasting is the difference in data format. Since digital broadcasting has no noise and distortion caused by the reflection of analog waves, it can reconstruct high-quality image and audio data and provide bi-directional service, not unidirectional service.
Furthermore, the digital broadcasting has an aspect ratio of 16:9 in consideration of the fact that human's eyes are more sensitive to lateral directions than to vertical directions. This ratio, that is, 16:9, is higher than the aspect ratio of the conventional analog broadcasting, that is, 4:3. Accordingly, viewers are under the illusion that they are provided with a screen wider than an actual screen.
Digital TV technology, that is, digital broadcasting, that provides image quality five times as high as that of conventional analog broadcasting is currently provided in some areas and coexists with analog broadcasting. However, the territory covered by digital broadcasting is continuously expanding.
Meanwhile, due to the coexistence of digital broadcasting with analog broadcasting, digital broadcasting stations transmit both High Definition (HD)-grade digital broadcasts having an aspect ratio of 16:9 and digital broadcasts having an aspect ratio of 4:3 when transmitting broadcast content.
The Standard Definition (SD)-grade digital broadcasts transmitted by the digital broadcasting stations have a digital format, into which analog broadcast data are converted, and an aspect ratio of 16:9, to which the analog broadcasts are extended.
Through a process of extending the aspect ratio of 4:3 to the aspect ratio of 16:9, images having an aspect ratio wider in a lateral direction than that of the original images are output.
FIG. 1 is a diagram illustrating the aspect ratios of a conventional analog broadcast and a digital broadcast.
As illustrated in the drawing, the aspect ratio of a conventional analog TV 11 is 4:3, whereas the aspect ratio of an HD-grade digital TV 12 is 16:9.
In this case, the resolution of the analog TV 11 is about 0.4 million pixels while the resolution of the HD-grade digital TV 12 is about 2 million pixels, so that the digital TV 12 has a resolution five times as high as that of the analog TV 11.
As shown in the drawing, when an HD-grade digital broadcast is displayed through the analog TV 11, an image is displayed with the sides thereof being eliminated due to the aspect ratio thereof.
FIG. 2 is a diagram illustrating a method of displaying a conventional analog broadcast on a digital TV.
Methods of displaying an analog broadcast having an aspect ratio of 4:3 on a digital TV using a display window having an aspect ratio of 16:9 include an up-scale scheme 21 and a crop scheme 22.
The up-scale scheme 21 is a method of extending an aspect ratio of 4:3 to an aspect ratio of 16:9, in which case an image stretched in a lateral direction is displayed due to the extension of the aspect ratio. Furthermore, since the analog TV has a resolution lower than that of the digital TV, digital image interpolation is performed to meet the resolution of the digital TV.
The crop scheme 22 is a method of displaying an image on a digital TV while maintaining an aspect ratio of 4:3, in which only digital image interpolation is performed, so that vacant spaces are produced on both sides of the display window of the digital TV having an aspect ratio of 16:9.
FIG. 3 is a diagram illustrating a method of displaying a digital broadcast on a conventional digital TV in the aspect ratio of digital broadcast.
A digital TV, having received an HD-grade digital broadcast, displays the digital broadcast having an aspect ratio of 16:9 in a display window. However, when the aspect ratio is set to 4:3, the digital broadcast is displayed in the set aspect ratio, in which case the above-described crop scheme is employed. Accordingly, the digital broadcast that is displayed in an aspect ratio of 16:9 is displayed in a form where images are vertically stretched (refer to reference numeral 31).
Accordingly, the users of digital TVs suffer inconvenience in that they must switch settings according to the aspect ratio of received broadcast content.
Moreover, there is no information about the aspect ratio in packets that are transmitted from a digital broadcasting station, so that it is difficult for a digital TV to automatically make settings.
Japanese Unexamined Pat. Pub. No. H05-292424 discloses an apparatus for receiving TV signals based on the NTSC standard, the EDTV standard and the digital TV standard and displaying broadcast content to meet respective standards. This invention supports only screen output, and provides no appropriate measure for dealing with aspect ratios.